1. Field of the Invention
The present invention relates to an automated warehouse system, and more particularly, to an automated warehouse system including a storage station, a retrieval station, a plurality of shelves, and a moving device.
2. Description of the Related Art
A conventional automated warehouse system has, for example, a pair of racks, a stacker crane, and storage and retrieval stations. The two racks are arranged so as to have a prescribed spacing in-between in a front-to-rear direction. The stacker crane is arranged such that it can move freely in a transverse direction between the front and rear racks. The storage station is arranged at a side of one of the racks, and the retrieval station is arranged at a side of the other of the racks. The racks have multiple article storage shelves arranged vertically and horizontally. The stacker crane has a travel unit, a hoist unit moving up and down a mast provided on the travel unit, and an article transferring unit (e.g., a sliding fork arranged such that it can freely slide back and forth) provided on the hoist unit.
A known example of such an automated warehouse system is a stocker used to store FOUPs (front opening unified pods) in a semiconductor manufacturing plant. With the stocker, during storage, an overhead conveying vehicle carries a FOUP into the storage station and a stacker crane carries the FOUP to a prescribed shelf. During retrieval, the stacker crane carries a FOUP from a prescribed shelf to the retrieval station and the overhead conveying vehicle carries the FOUP away from the retrieval station.
Since a conveying performance of the stocker is lower than a conveying performance of the overhead conveying vehicle, the article conveying performance of the plant as a whole declines. Therefore, improvements have been made to a shelf determining method of the automated warehouse system in order to increase the conveying performance of the stocker.
A conventional automated warehouse shelf determining method will now be explained. The shelves of the automated warehouse system are divided into a plurality of blocks based on distances from the station to the shelves, and the articles that are stored and retrieved to and from the automated warehouse system are categorized based on a frequency of storage and retrieval in accordance with the number of the blocks. When articles are stored into the warehouse, articles having a high storage-retrieval frequency are assigned to a shelf in a block that is closer to the station. (See, for example, Japanese Laid-open Patent Publication No. 3-8602).
With the conventional automated warehouse shelf determining method explained above, it is necessary to acquire information related to the storage-retrieval frequency of the article in advance. Since it is necessary to obtain special information from other equipment, a cycle efficiency of storage and retrieval cannot be sufficiently increased in a conventional automated warehouse system.